Utility vehicles, such as lawn and garden tractors and mowers, have generally relied upon internal combustion engines as the prime mover transferring power through mechanical linkages (gearing or belts), hydrostatic drive(s) or other similar devices to propel or drive the vehicle. A deck of the utility vehicle is typically used to employ an auxiliary system, such as cutting blades of a lawn tractor. The majority of commercial and consumer mowers employ a deck (auxiliary) drive system using belts and pulleys driven by an engine typically with an electric clutch/brake to stop or drive the deck system. Other variants take the form of a power take off (PTO) shaft in combination with pulleys and belts to drive multiple blade spindles in larger decks or to individually drive spindles with hydraulic motors in multiple deck or reel versions.
Utility vehicles and other equipment incorporating electric motor(s) as primary mover(s) have emerged as viable alternatives to internal combustion utility vehicles and equipment, particularly due to rising oil and fuel prices. Consumers also want products with increased comfort and increasing versatility in smaller packages. Electric vehicles offer considerable advantages for reduction of emission of noise and pollution, as well as improved operator controls. These vehicles, which typically include one or more work accessories or auxiliary systems incorporating additional electric motors, also incorporate various forms and levels of control, depending upon the vehicle type, drive type, functional features, and other design aspects to ensure safe operation. With the advancement of these vehicle types and their functionality, various problems and needs have arisen in their design, operation, and functionality.
Due to their relative high power capacity, three-phase AC electric motors are typically used in utility vehicles to drive axle shafts or work implements and are powered by a power source, such as an on-board battery pack or array. AC induction motors, and Permanent Magnet Synchronous (PMS) Motors in particular, would be advantageous in utility vehicle applications due to their power capacities and efficiencies in their physical constructions. PMS motors have the ability to rapidly accelerate and decelerate high-inertial loads, which minimizes processing time. Both AC induction motors and PMS motors utilize a stator assembly with specially distributed phase windings connected in either a “wye” or “delta” fashion. Stator laminations minimize airgap reluctance, facilitating a high level of flux coupling between the rotor and stator. The magnetic circuit of the PMS motor is similar to an AC induction motor. The fundamental difference between PMS and AC induction is how magnetic poles are produced on the rotor. An AC induction motor induces magnetic poles that travel along the rotor's surface, a process that requires a small airgap and consumes a component of applied motor power. Conversely, PMS motors create stationary poles on the rotor using fixed high-energy magnets. Permanent magnet rotor construction supports larger airgaps, reduces the rotor's inertia, and increases motor efficiency by eliminating power consumption associated with AC induction. Due to these advantages, PMS motors offer significant potential advantages in utility vehicle applications.
Regardless of the motor type, however, implementation to power auxiliary functions of utility vehicles presents a variety of problems. These vehicles often operate in harsh environments that could damage the motor if it is not adequately protected. Furthermore, there is a problem in balancing the need for powerful electric motors with accommodating these powerful motors in a vehicular application, which typically places a premium on reducing size and weight of components. The physical dimensions and overall size of standard off-the-shelf motors that have the required power capacities many times present clearance problems for the vehicle designer or obstructions to the vehicle operator. Presently available off-the-shelf motor designs that provide sufficient torque are often too large and/or too heavy to be practical for application to a utility vehicle. Additionally, they may not be configured in a suitable manner to drive the required auxiliary implement(s). With the advancement of electric-drive utility vehicles and their functionality, the aforementioned problems, as well as other problems and needs have arisen. This disclosure is directed to addressing these and other problems in the general area of improved electric motor design and drive configurations for utility vehicle applications.